bims-unfpre 2023-01-08 papers

bims-unfpre

Biomed News

on Unfolded protein response

Issue of 2023–01–08
nine papers selected by
Susan Logue, University of Manitoba

The endoplasmic reticulum kinase PERK interacts with the oxidoreductase ERO1 to metabolically adapt mitochondria.
Increased interaction between endoplasmic reticulum and mitochondria following sleep deprivation.
The transcription factor ATF4 mediates endoplasmic reticulum stress related podocyte injury and slit diaphragm defects.
The functional implication of ATF6α in castration-resistant prostate cancer cells.
Deletion induced splicing in RIC3 drives nicotinic acetylcholine receptor regulation with implications for endoplasmic reticulum stress in human astrocytes.
Hsp27, Hsp60, Hsp70, or Hsp90 depletion enhances the antitumor effects of resveratrol via oxidative and ER stress response in human glioblastoma cells.
The role of unfolded protein response-associated miRNAs in immunogenic cell death amplification: A literature review and bioinformatics analysis.
Endoplasmic reticulum stress mediates the myeloid-derived immune suppression associated with cancer and infectious disease.
Hepatic SEL1L-HRD1 ER-associated degradation regulates systemic iron homeostasis via ceruloplasmin.

Cell Rep. 2022 Dec 23. pii: S2211-1247(22)01798-3. [Epub ahead of print] 111899

The endoplasmic reticulum kinase PERK interacts with the oxidoreductase ERO1 to metabolically adapt mitochondria.

Arthur Bassot, Junsheng Chen, Kei Takahashi-Yamashiro, Megan C Yap, Christine Silvia Gibhardt, Giang N T Le, Saaya Hario, Yusuke Nasu, Jack Moore, Tomas Gutiérrez, Lucas Mina, Heather Mast, Audric Moses, Rakesh Bhat, Klaus Ballanyi, Hélène Lemieux, Roberto Sitia, Ester Zito, Ivan Bogeski, Robert E Campbell, Thomas Simmen.

  Endoplasmic reticulum (ER) homeostasis requires molecular regulators that tailor mitochondrial bioenergetics to the needs of protein folding. For instance, calnexin maintains mitochondria metabolism and mitochondria-ER contacts (MERCs) through reactive oxygen species (ROS) from NADPH oxidase 4 (NOX4). However, induction of ER stress requires a quick molecular rewiring of mitochondria to adapt to new energy needs. This machinery is not characterized. We now show that the oxidoreductase ERO1⍺ covalently interacts with protein kinase RNA-like ER kinase (PERK) upon treatment with tunicamycin. The PERK-ERO1⍺ interaction requires the C-terminal active site of ERO1⍺ and cysteine 216 of PERK. Moreover, we show that the PERK-ERO1⍺ complex promotes oxidization of MERC proteins and controls mitochondrial dynamics. Using proteinaceous probes, we determined that these functions improve ER-mitochondria Ca2+ flux to maintain bioenergetics in both organelles, while limiting oxidative stress. Therefore, the PERK-ERO1⍺ complex is a key molecular machinery that allows quick metabolic adaptation to ER stress.

Keywords:  CP: Metabolism; CP: Molecular biology; ER; ER stress; ERO1; MAMs; MERCs; PERK; bioenergetics; endoplasmic reticulum; mitochondria; mitochondria-associated membranes; mitochondria-endoplasmic reticulum contacts; oxidoreductase

DOI:  https://doi.org/10.1016/j.celrep.2022.111899
BMC Biol. 2023 Jan 04. 21(1): 1

Increased interaction between endoplasmic reticulum and mitochondria following sleep deprivation.

Amina Aboufares El Alaoui, Edgar Buhl, Sabrina Galizia, James J L Hodge, Luisa de Vivo, Michele Bellesi.

   BACKGROUND: Prolonged cellular activity may overload cell function, leading to high rates of protein synthesis and accumulation of misfolded or unassembled proteins, which cause endoplasmic reticulum (ER) stress and activate the unfolded protein response (UPR) to re-establish normal protein homeostasis. Previous molecular work has demonstrated that sleep deprivation (SD) leads to ER stress in neurons, with a number of ER-specific proteins being upregulated to maintain optimal cellular proteostasis. It is still not clear which cellular processes activated by sleep deprivation lead to ER- stress, but increased cellular metabolism, higher request for protein synthesis, and over production of oxygen radicals have been proposed as potential contributing factors. Here, we investigate the transcriptional and ultrastructural ER and mitochondrial modifications induced by sleep loss.
RESULTS: We used gene expression analysis in mouse forebrains to show that SD was associated with significant transcriptional modifications of genes involved in ER stress but also in ER-mitochondria interaction, calcium homeostasis, and mitochondrial respiratory activity. Using electron microscopy, we also showed that SD was associated with a general increase in the density of ER cisternae in pyramidal neurons of the motor cortex. Moreover, ER cisternae established new contact sites with mitochondria, the so-called mitochondria associated membranes (MAMs), important hubs for molecule shuttling, such as calcium and lipids, and for the modulation of ATP production and redox state. Finally, we demonstrated that Drosophila male mutant flies (elav > linker), in which the number of MAMs had been genetically increased, showed a reduction in the amount and consolidation of sleep without alterations in the homeostatic sleep response to SD.
CONCLUSIONS: We provide evidence that sleep loss induces ER stress characterized by increased crosstalk between ER and mitochondria. MAMs formation associated with SD could represent a key phenomenon for the modulation of multiple cellular processes that ensure appropriate responses to increased cell metabolism. In addition, MAMs establishment may play a role in the regulation of sleep under baseline conditions.

Keywords:  Brain; Drosophila; Electron microscopy; Mouse; Neuron; Sleep deprivation

DOI:  https://doi.org/10.1186/s12915-022-01498-7
Kidney Int. 2022 Dec 29. pii: S0085-2538(22)01088-2. [Epub ahead of print]

The transcription factor ATF4 mediates endoplasmic reticulum stress related podocyte injury and slit diaphragm defects.

Vanessa Krausel, Lisanne Pund, Harald Nüsse, Hussein Bachir, Andrea Ricker, Jürgen Klingauf, Thomas Weide, Hermann Pavenstädt, Michael P Krahn, Daniela A Braun.

  Mutations in OSGEP and four other genes that encode subunits of the KEOPS complex cause Galloway-Mowat syndrome, a severe, inherited kidney-neurological disease. The complex catalyzes an essential posttranscriptional modification of tRNA and its loss of function induces endoplasmic reticulum (ER) stress. Here, using Drosophila melanogaster garland nephrocytes and cultured human podocytes, we aimed to elucidate the molecular pathogenic mechanisms of KEOPS related glomerular disease and to test pharmacological inhibition of ER stress related signaling as a therapeutic principle. We found that ATF4, an ER stress mediating transcription factor, or its fly orthologue Crc, were upregulated in both fly nephrocytes and human podocytes. Knockdown of Tcs3, a fly orthologue of OSGEP, caused slit diaphragm defects, recapitulating the human kidney phenotype. OSGEP cDNA with mutations found in patients lacked the capacity for rescue. Genetic interaction studies in Tcs3 deficient nephrocytes revealed that Crc mediates not only cell injury, but surprisingly also slit diaphragm defects, and that genetic or pharmacological inhibition of Crc activation attenuates both phenotypes. These findings are conserved in human podocytes where ATF4 inhibition improved the viability of podocytes with OSGEP knockdown, with chemically-induced ER stress, and where ATF4 target genes and pro-apoptotic gene clusters are upregulated upon OSGEP knockdown. Thus, our data identify ATF4 mediated signaling as a molecular link between ER stress, slit diaphragm defects, podocyte injury, and suggest that modulation of ATF4 signaling may be a potential therapeutic target for certain podocyte diseases.

Keywords:  Drosophila nephrocyte; endoplasmic reticulum stress; molecular therapeutic target; podocyte injury; slit diaphragm defect

DOI:  https://doi.org/10.1016/j.kint.2022.11.024
FASEB J. 2023 Feb;37(2): e22758

The functional implication of ATF6α in castration-resistant prostate cancer cells.

Hongqing Zhou, Tingting Zhang, Liang Chen, Fengzhen Cui, Chenxiang Xu, Jiaxi Peng, Weixiang Ma, Jirong Huang, Xia Sheng, Mingsheng Liu, Faming Zhao.

  Stress in the endoplasmic reticulum (ER) may perturb proteostasis and activates the unfolded protein response (UPR). UPR activation is frequently observed in cancer cells and is believed to fuel cancer progression. Here, we report that one of the three UPR sensors, ATF6α, was associated with prostate cancer (PCa) development, while both genetic and pharmacological inhibition of ATF6α impaired the survival of castration-resistance PCa (CRPC) cells. Transcriptomic analyses identified the molecular pathways deregulated upon ATF6α depletion, and also discovered considerable disparity in global gene expression between ATF6α knockdown and Ceapin-A7 treatment. In addition, combined analyses of human CRPC bulk RNA-seq and single-cell RNA-seq (scRNA-seq) public datasets confirmed that CRPC tumors with higher ATF6α activity displayed higher androgen receptor (AR) activity, proliferative and neuroendocrine (NE) like phenotypes, as well as immunosuppressive features. Lastly, we identified a 14-gene set as ATF6α NE gene signature with encouraging prognostic power. In conclusion, our results indicate that ATF6α is correlated with PCa progression and is functionally relevant to CRPC cell survival. Both specificity and efficacy of ATF6α inhibitors require further refinement and evaluation.

Keywords:  ATF6α; CRPC; ER stress; UPR; prostate cancer

DOI:  https://doi.org/10.1096/fj.202201347R
Glia. 2023 Jan 05.

Deletion induced splicing in RIC3 drives nicotinic acetylcholine receptor regulation with implications for endoplasmic reticulum stress in human astrocytes.

Navneesh Yadav, B K Thelma.

  Nicotinic acetylcholine receptor (nAChR) dysregulation in astrocytes is reported in neurodegenerative disorders. Modulation of nAChRs through agonists confers protection to astrocytes from stress but regulation of chaperones involved in proteostasis with pathological implications is unclear. Resistance to inhibitors of cholinesterase 3 (RIC3), a potential chaperone of nAChRs is poorly studied in humans. We characterized RIC3 in astrocytes derived from an isogenic wild-type and Cas9 edited "del" human iPSC line harboring a 25 bp homozygous deletion in exon2. Altered RIC3 transcript ratio due to deletion induced splicing and an unexpected gain of α7nAChR expression were observed in "del" astrocytes. Transcriptome analysis showed higher expression of neurotransmitter/G-protein coupled receptors mediated by cAMP and calcium/calmodulin-dependent kinase signaling with increased cytokines/glutamate secretion. Functional implications examined using tunicamycin induced ER stress in wild-type astrocyte stress model showed cell cycle arrest, RIC3 upregulation, reduction in α7nAChR membrane levels but increased α4nAChR membrane expression. Conversely, tunicamycin-treated "del" astrocytes showed a comparatively higher α4nAChR membrane expression and upsurged cAMP signaling. Furthermore, reduced expression of stress markers CHOP, phospho-PERK and lowered XBP1 splicing in western blot and qPCR, validated by proteome-based pathway analysis indicated lowered disease severity. Findings indicate (i) a complex RNA regulatory mechanism via exonic deletion induced splicing; (ii) RIC-3 as a disordered protein having contrasting effects on co-expressed nAChR subtypes under basal/stress conditions; and (iii) RIC3 as a potential drug target against ER stress in astrocytes for neurodegenerative/nicotine-related brain disorders. Cellular rescue mechanism through deletion induced exon skipping may encourage ASO-based therapies for tauopathies.

Keywords:  RIC3; astrocytes; endoplasmic reticulum stress; nicotinic acetylcholine receptors; splicing

DOI:  https://doi.org/10.1002/glia.24333
Biochem Pharmacol. 2023 Jan 02. pii: S0006-2952(22)00505-6. [Epub ahead of print] 115409

Hsp27, Hsp60, Hsp70, or Hsp90 depletion enhances the antitumor effects of resveratrol via oxidative and ER stress response in human glioblastoma cells.

Evren Önay-Uçar, Aslıhan Şengelen, Elif Mertoğlu-Kamali.

  Therapeutic resistance of gliomas is still a crucial issue and closely related to induced heat shock response (HSR). Resveratrol (RSV) is a promising experimental agent for glioblastoma (GB) therapy. However, the role of heat shock protein (Hsp)27, Hsp60, Hsp70, and Hsp90 on the therapeutic efficacy of RSV remains unclear in gliomas. Herein, small interfering (si)RNA transfection was performed to block Hsp expressions. RSV treatments reduced glioma cells' viability dose- and time-dependent while keeping HEK-293 normal cells alive. Furthermore, a low dose of RSV (15 µM/48h) offered protection against oxidative stress and apoptosis due to Hsp depletion in healthy cells. On the contrary, in glioma cells, RSV (15 µM/48h) increased ROS (reactive oxygen species) production, led to autophagy and induced endoplasmic reticulum (ER) stress and apoptosis, and reduced 2D- and 3D-clonogenic survival. Hsp27, Hsp60, Hsp70, or Hsp90 depletion also resulted in cell death through ER stress response and ROS burst. Remarkably, the heat shock response (increased HSF1 levels) due to Hsp depletion was attenuated by RSV in glioma cells. Collectively, our data show that these Hsp silencings make glioma cells more sensitive to RSV treatment, indicating that these Hsps are potential therapeutic targets for GB treatment.

Keywords:  Apoptosis; Glioma; Heat shock protein (Hsp); Hsp silencing; Resveratrol

DOI:  https://doi.org/10.1016/j.bcp.2022.115409
Life Sci. 2022 Dec 29. pii: S0024-3205(22)01041-4. [Epub ahead of print]314 121341

The role of unfolded protein response-associated miRNAs in immunogenic cell death amplification: A literature review and bioinformatics analysis.

Mahdieh Azizi, Sadra Salehi-Mazandarani, Parvaneh Nikpour, Alireza Andalib, Marzieh Rezaei.

  Immunogenic cell death (ICD) is a type of cellular death that is elicited in response to the specific types of anti-cancer therapies and enhances the anti-tumor immune responses by the combination of antigenicity and adjuvanticity of dying tumor cells. There is a well-established interlink between endoplasmic reticulum stress (ERS) and ICD elicited by anti-cancer therapies. Most recent evidences support that unfolded protein response (UPR)-associated miRNAs can be key players in the ERS-induced ICD. Hence, in the present study, we conducted a literature review on the role of these miRNAs and associated molecular pathways that may regulate ICD. We first collected UPR-associated miRNAs that promote ERS-induced apoptosis and then focused on microRNAs (miRNAs) that promote ERS-induced apoptosis via PERK/eIF2α/ATF4/CHOP pathway activation, as the main core for ICD and release of damage-associated molecular patterns. To better identify PERK/eIF2α/ATF4/CHOP pathway-inducing miRNAs that can be used as potential therapeutic targets for improving ICD in cancer treatment, we did a comprehensive bioinformatics analysis and network construction. Our results showed that "pathways in cancer", "MAPK signaling pathway", "PI3K-Akt signaling pathway", and "Cellular senescence", which correlate with UPR components and ERS induction, were among the significant signaling pathways related to the target genes of these miRNAs. Furthermore, a protein-protein interaction (PPI) network was constructed, which revealed the involvement of the PPI-extracted hub genes in the regulation of proliferation and apoptosis. In conclusion, we propose that these types of miRNAs can be considered as the potential cancer therapy options for better induction of ICD in combination with other ICD inducers.

Keywords:  Bioinformatics; Cancer therapy; Endoplasmic reticulum stress; Immunogenic cell death; Unfolded protein response; miRNAs

DOI:  https://doi.org/10.1016/j.lfs.2022.121341
J Transl Med. 2023 Jan 02. 21(1): 1

Endoplasmic reticulum stress mediates the myeloid-derived immune suppression associated with cancer and infectious disease.

Xiaoli Lou, Deyong Gao, Liyuan Yang, Yue Wang, Yanqiang Hou.

  Myeloid-derived suppressor cells (MDSCs), which are immature heterogeneous bone marrow cells, have been described as potent immune regulators in human and murine cancer models. The distribution of MDSCs varies across organs and is divided into three subpopulations: granulocytic MDSCs or polymorphonuclear MDSCs (G-MDSCs or PMN-MDSCs), monocytic MDSCs (M-MDSCs), as well as a recently identified early precursor MDSC (eMDSCs) in humans. Activated MDSCs induce the inactivation of NK cells, CD4+, and CD8+ T cells through a variety of mechanisms, thus promoting the formation of tumor immunosuppressive microenvironment. ER stress plays an important protecting role in the survival of MDSC, which aggravates the immunosuppression in tumors. In addition, ferroptosis can promote an anti-tumor immune response by reversing the immunosuppressive microenvironment. This review summarizes immune suppression by MDSCs with a focus on the role of endoplasmic reticulum stress-mediated immune suppression in cancer and infectious disease, in particular leprosy and tuberculosis.

Keywords:  Cancer; Endoplasmic reticulum stress; Immune suppression; Leprosy and tuberculosis; Myeloid-derived suppressor cells

DOI:  https://doi.org/10.1186/s12967-022-03835-4
Proc Natl Acad Sci U S A. 2023 Jan 10. 120(2): e2212644120

Hepatic SEL1L-HRD1 ER-associated degradation regulates systemic iron homeostasis via ceruloplasmin.

Pattaraporn Thepsuwan, Asmita Bhattacharya, Zhenfeng Song, Stephen Hippleheuser, Shaobin Feng, Xiaoqiong Wei, Nupur K Das, Mariana Sierra, Juncheng Wei, Deyu Fang, Yu-Ming M Huang, Kezhong Zhang, Yatrik M Shah, Shengyi Sun.

  Iron homeostasis is critical for cellular and organismal function and is tightly regulated to prevent toxicity or anemia due to iron excess or deficiency, respectively. However, subcellular regulatory mechanisms of iron remain largely unexplored. Here, we report that SEL1L-HRD1 protein complex of endoplasmic reticulum (ER)-associated degradation (ERAD) in hepatocytes controls systemic iron homeostasis in a ceruloplasmin (CP)-dependent, and ER stress-independent, manner. Mice with hepatocyte-specific Sel1L deficiency exhibit altered basal iron homeostasis and are sensitized to iron deficiency while resistant to iron overload. Proteomics screening for a factor linking ERAD deficiency to altered iron homeostasis identifies CP, a key ferroxidase involved in systemic iron distribution by catalyzing iron oxidation and efflux from tissues. Indeed, CP is highly unstable and a bona fide substrate of SEL1L-HRD1 ERAD. In the absence of ERAD, CP protein accumulates in the ER and is shunted to refolding, leading to elevated secretion. Providing clinical relevance of these findings, SEL1L-HRD1 ERAD is responsible for the degradation of a subset of disease-causing CP mutants, thereby attenuating their pathogenicity. Together, this study uncovers the role of SEL1L-HRD1 ERAD in systemic iron homeostasis and provides insights into protein misfolding-associated proteotoxicity.

Keywords:  SEL1L-HRD1 ERAD; ceruloplasmin; hepatocytes; iron metabolism

DOI:  https://doi.org/10.1073/pnas.2212644120